Function mutex_fast_lock

examples/stdlib.c:1507–1511

#endif      /* MUTEX_SAFE */

static bool mutex_fast_lock(pid_t self, pid_t *x)
{
    pid_t owner = __sync_val_compare_and_swap(x, 0, self);
    return (owner == 0);
}

static bool mutex_fast_unlock(pid_t self, pid_t *x)
{